The present invention relates to a case mounting mechanism, and more particularly to a case mounting mechanism for use with a pneumatic device such as a filter, a lubricator or the like which has a case guard for protecting a case in surrounding relation, the case mounting mechanism being capable of easily mounting the case guard and the case together on a body of the device and of preventing the case or the case guard from being easily detached from the body when there is a pressure in the case.
Pneumatic devices such as filters and lubricators have a case mounted on a body and accommodating a filter element or lubricating oil. The case is made of a transparent or semitransparent material to allow the user to visually check the amount of drain or lubricating oil in the case. Since the transparent or semitransparent material for the case is normally synthetic resin molded into a required shape, the case does not have a sufficient degree of mechanical strength. Therefore, the case is protected by a case guard of metal which surrounds the case.
When it is necessary to clean, replace, or otherwise service the case, the case and the case guard have to be detached from the body. If an attempt is made to remove the case from the body without confirming absence of an air pressure in the case when there is in fact a high air pressure remaining in the case, the case or the case guard is forced to fly apart from the body, resulting in the danger of damage to the operator and/or surrounding devices.
As a safeguard against such damage, the case or the case guard is mounted on the body in threaded engagement according to one conventional design. This arrangement is however disadvantageous in that it takes time to mount the case and the case guard on the body or detach them from the body, and also in that the body, the case, and the case guard are structurally complex and costly to manufacture since screw threads have to be formed on them.
The case and the case guard are inherently separate from each other. If they are detached from each other when they are dismounted from the body, the case may inadvertently drop off the case guard and may be broken upon hitting engagement with other object since the case of synthetic resin is relatively fragile.